Telephone system



June ll, 1929. H. D. cAHlLl.

TELEPHONE SYSTEM 'A 2 Shets-Sheet 2 Filed Nov. 30, 1926 llHlI Patented June 1l, 19279.

UNITED vSTATES*PATENT OFFICE- HAROLD D. CAHILL, F BROOKLYN, NEW YORK, ASSIGNOR To BELL TELEPHONE LAB- ORATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Application filed November 30, 1926. Serial No. 151,631.

This invention relates to telephone systems and more particularly to straightforward trunki ng systems.

According to this invention a straightforward trunking system is arranged so that the ringing equipment of a trunk, which has been set by the operation of a ringing key equipment common to a plurality of trun-s at a B operators position, started in response to a signal applied to the trunk at its originating end by the originating operator and in response to the connection of the trunk at the B operators position to a. wanted subscribers line.

The invention may be applied to straightforward trunking systems of the kind described in Patent No. 1,667,830 granted to Horace W. Ulrich May 1, 1928, in which there is provided circuit means whereby a ringing key equipment and a B operators telephone set, common to a plurality of trunks are adapted to be associated with the incoming end of any one of said trunks. This means operates if a trunk has been seized by an A r operator at its outgoing end and a key individual to this trunk has been actuated. The B operators telephone set is associated with the trunk to enable the B operator to communicate with the A operator and the common ringing key equipment is associated with the trunk to control or set a ringing' circuit equipment, individual to the trunk in accordance with the setting of its keys for the transmission of a corresponding ringing signal to a line in response to its subsequent connection to the trunk by the B operator.

The present invention is particularly adaptable for use in straightforward trunking systems where the trunks are toll switching trunks extending from toll operators positions, and where it is consequently necessary to delay ringing the wanted subscriber until the toll operator has completed the connection to the calling subscriber as is well known in the art.

This invent-ion has been illust-rated in the accompanying drawings in which Fig. l shows a. straightforward trunk of the toll switching trunk type embodying the features of this invention. This trunk is shown originating at a toll operators position where a toll operators cord is shown in diagrammatic form for completing connections to a calling subscriber at a distant office. This straightforward trunk is shown terminating in a plug at a B operators position and a called subscribers line has also been shown in this ligure in diagrammatic form. Fig. 2 shows a comlnon ringing key equipment and a B operators telephone set which may be associated with any one of the trunks of a groupof trunks of which the straightforward trunk shown in Fig. 1 is representative.

Referringvnow to the drawings it is assumed that a toll operator at A has inserted the calling plug of a cord l into jack 2 of trunk ST that terminates ata B operators position. The following description will relate to the association of the common ringing key equipment shown in Fig. 2 with this trunk and to the manipulation of the ringing keys thereofA to prepare the usual ringing ke equipment associated with the trunk ST for the transmission of ringing signals to a wanted subscribers line, such as line 3. This description will explain how the ringing equipment of trunk ST is operated to transmit a ringing signal to the subscriber of line 3 in response to the connection of plug 4 of trunk ST into jack 5 of line 3 and to the reception of an alternating current signal from the toll operator at A. l Y

When trunk ST is seized it is well-known in the art how a loop circuit is established through the cord 1 for the operation of relay 6 in the trunk ST. Relay 6 in operating closes a circuit for the operation of relay 7 as follows: Battery, inner upper armature and back contact of relay 10, left-hand winding of relay 7 to ground at the 'armature and front contact of relay 6. Relay 6 in operating also closes an obvious circuit for the operation of relay 8. Relay 8 in operating closes a circuit for the operation of relay 9 as follows: Battery, make-before-break contacts of relay 11, upper winding of relay 9, inner lower armature and back contact of relay 10, armature and front contact of relay 8 to ground.

Relay 9l in operating closes a. circuit for lay 100, right-hand winding of relay 101 to ground. This circuit causes the lighting of lamp 12 and the operation of relay 101. Relay 101 in operating closes an obvious circuit for the operation or the slow-to-operate relay 102. This relay in turn closes an obvious circuit for the slow-to-operate relay 103. v Relay 103 in operating closes an obvious circuit for the operation ot slow-to-operate relay which in operating inserts a resistance in the circuit tor lamp 12 and at the same time places a shunt about the said resistance and lamp 12 comprising the lett hand winding et' relay 101 whereby lamp 12 is now extinguished. On the operation of this relay 100, the circuit through the right-hand winding or relay 101 is extended 'through the makebeiore-break contacts ot relay 100 through the left-hand winding of relay 101 'to battery. This relay is therefore maintained operated even though relay 100 lis operated. Gn the operation of relay 100, the'circuit for relay 102 is opened at the right-hand armature and back contact oit this relay and relay 102 in releasing causes the release o1a relay 103 and Vrelay 103 releases relay 100. Un the release of relay 100 the original circuit tor lamp 12 is reestablished so that this lamp is again lighted and the operations and release ot relays 100, 102 and 103 are repeated in this manner so as to alternately light and extinguish lamp 12. The flashing o'lE lamp 12 indicates to the B operator in charge of trunk ST that a connection over this trunk is desired. The operyation ol relay 9 also closes at its lower armature a circuit-tor the subsequent operation of vrelay 18 as will hereinafter be described.

The B operator new depresses key 20 to associate the common ringing key equipment and her telephone set with this trunk. rllhe operation ot key 20 closes the circuit previously prepared by the operation ot relay 9 for the operation of relay 18 as fellows: Battery, niake-before-break contacts et relay 11, lower armature and trent contact et relay 9, winding et relay 18, key 20, lead 23, letthand armature and back contact ot relay 10G yto ground. Relay 18 in operating provides a locking circuit Y1:01' itseltl after the release et key V20 independent oit the circuit through key 2O over its upper inner armature and front contactthrough lead 25, winding of rclay 108, armature and back contact ot relay 109 to ground. It should be noted that'this locking circuit for relay 18 is also provided for the locking oit relay 9 by a circuit through the lower winding of relay 9 which circuit is Ain parallel with the circuit through the winding oit relay 18, and that relay 108 is operated by the subsequent release of key 20. `Relay 108 in operating lights a lamp 110 which indicates that this common ringing key equip- Vment will be used by the B operator. more complete description 01": the specific purpose of the lighting ot this lamp, re't'ercnce For a may be had to the above mentioned copending application ot Horace W. Ulrich. The operation oi relay 108 also causes an obvious circuit to be closed for the operation of relay 100 and relay 106 in operating closes an obvious circuit for the operation ot relay 112. Relay 112 in operating closes a circuit for the lighting ot' lamp 113 to indicate to the-B operator that her telephone set 115 and the common ringing key equipment, generally indicated by the numeral 116, have been connected to a trunk. The connection et these equipments to the trunk is established through the operation of relay 18.

rIhe operation. of relay 106 removes the ground, at its lett-hand armature and back contact for the original energizing circuit for relay 18 and as lead 23 is common to all trunks in the group oit which trunk ST is one, the common ringing key equipment and the operators telephone set cannot be associated with any other trunk in this group as long relay 18 ot trunk ST is operated that is, only one trunk at a time can be associated withV these common equipments.

r1`he operator-s'telephone set. 115 and the common ringing key equipment 11G are connected to trunk ST and a si u1al is transmitted to the toll operators cord 1 at A to indicate that the B operator is ready to receive the information relating to the extension of a call as follows: The signalconsists of two successive applications of tone current 'from a source 118. Upon the operation of relay 100 a circuit is closed for the operation ot relay 119 as follows Battery, winding et relay 119, lower outer armature and back contact ot relay 120, lower armature and 'front contact ot vrelay 121, lett-hand armature and 'front centact ot' relay 10G4 to ground. lt should be noted that this circuit is traced through the Vlower armature and front Contact of relay 121. It is evident, by examining the circuits in this drawing, that this relay is operated as soon as the operators telephone set 115 is connected through jacks and plugs 122 to the repeating coil 123. That is, when this connection is made a circuit is completed ttor the operation of relay 124 through the operators transmitter. The operation of relay 121 closes an obvious circuit for the operation ot relay 121. Hence these two relays remain operated as long as the operators telephone set is connected at this point. rllhe relay 119 in operating connects the secondary winding of repeating coil 126 to the tip and ring leads now connected through the operation et relay 119 to the conductors ot trunk ST. his circuit niay be traced 'from the tip and ring conductors of trunk ST through the upper outer and lower outer armatures and trout conta ets of relay 18, tip and ring conductors 27 and 28, upper outer and lower inner armatures and 'back contacts ot relay 120, upper outer and lli tures and front contacts of relay 119 to the secondary winding of repeating coil 126. The primary7 winding of this repeating coil is connected by the operation of relay 119 as follows: Ground, secondary winding of repeating coil 118, primary winding ot repeating coil 126, lower outer armature and front contact of relay 119, make-before-break contacts ol. relay 130, lower armature and back contact ot relay 131, upper inner armature and back contact of relay 127 to ground at the inner upper armature and front cont-act ot' relay 119. The secondary winding of repeating coil 118 is associated with the tone source 118 so that an impulse of' tone current is now transmitted trom this source through trunk ST to the toll operators telephone set connected to cord 1.

The operation of relay 119 also closes an obvious circuit for slow-to-operate relay 130. This relay in operating opens the circuit tor the secondary winding of repeating coil 118 and primary winding of repeating coil 126 Vso that the impulse of tone current applied through these windings to the trunk ST is presently cut ott.

The operation of relay 130 closes an'obvious circuit 'tor the operation ot' slow-to-operate relay 132. Relay 132 in operating again conipletes a coupling between the ringing source 118 and the secondary winding of repeatingcoil 126 by closing a circuit that now exteiuls through the lower armature and front contact of relay 130, the lower armature and front contact of relay 132 through the lower armature and back Contact ot relay 131. Hence, a second application ot tone current trom source 118 is now effected.

Relay 132 also closes an obvious circuit for the operation of the slow-to-operate relay 131. On the operation ot this relay, the circuit 'tor the secondary winding oit repeating Coil 118 and the primary winding oli repeatingcoil 126 is again opened, this time at the lower armature and back contact of relay 131. Consequently, the second impulse of tone current-is there y presently removed from the trunk. The operation of relay 131 closes an obvious circuit for the operation of relay 127 and this relay in operating closes a locking circuit tor itself to `ground at the upper inner armature and front contact of relay 119. Relay 127 operated opens a connection from the secondary winding of repeating coil 126 to the tip and ring conductors of the trunk and also the original circuit through the secondary winding ot repeating coil 11S-and primary winding of repeating coil 126. As long as rela y 119 is operated no further application ot tone current will therefore be made during the connection of'the circuits shown in Fig. 2 to the trunk ST. On the operation ot relay 127 the operators telephone set 115 is connected through the repeating coil 123 to the tip and ring conductors of trunk ST at the upper outer and inner lowery armatures and front contacts of relay 127.

The operation of relay 18 connects certain other leads between the common ringing equipment and the trunk ST such as leads 36, 37 and 38 for the control of the ringing equipment associated with the trunk by manipulations of the ringing keys 116.

As the B operators telephone set is now connected to the trunk and the toll operator at. A has received a signal to this efect, this latter operator will pass the information relative to the extension of a connection by the B operator and when this information is received, the B operator will operate a corresponding key in the ringing key equipment. If the party wanted is one on a party line, one of the keys 140, 141, 142 or 143 is operated whereas if the call is to be advanced over an automatic trunk when machine ringing is not required, key 144 is operated.

If a party M is desired, key 140 is depressed to prepare the ringing equipment associated with the trunk ST for the sending of the proper signal. lVhen key 140 is depressed relay 146 is actuated over` an obvious circuit. This relay in operating prepares a locking circuit for itself through its right-hand armature and front contact to ground at the inner left-hand armature and front contact of relay 112. The operation of relay 146 completes circuits for the operation of relays 43 and 44. A circuit 'for relay 43 may be traced as follows: Battery, Winding of relay 43, lower middle armature and front Contact of relay 18, lead 36, lefthand armature and a front contact of relay 146 to ground at relay 112, while the circuit for relay 44 may be traced from battery, through the Winding of relay 44, lower inner armature and front contact of relay 18, conductor 38, lett-hand armature and a front contact of relay 146 to ground at relay 112. Relays 43 and 44 provide locking circuits for themselves through their lower armatures and front contacts to ground at the armature and front contact of relay 41, when this relay operates as will be described hereinafter. The operation of relays 43 and 44 causes circuits from the ringing source 46 and from ground to be completed for the application of ringing current to the conductors of trunk ST as follows: Source 46, winding of tripping relay 40, upper armature and front contact of relay 43, lower outer armature and front contact of relay 11, when this relay operates as will be presently described, upper inner armature and front contact of relay 44 to the front contact associated with the upper armature ot' relay 47 connected to the tip conductorof trunk ST, and from ground, upper vouter armature and front contact of vrelay 44 to the front contact associated with the lower armature of relay 47 connected to the ringl conductor ot' trunk ST. The operation oi relay 146 also closes a circuit for the operation oi the sloW-to-operate relay 1&7 as tellows :A Battery, Winding` oli' relay 14,7, righthand armature and a trout Contact ot relay 14:6 to ground at the inner lett-hand arman ture and trent Contact et relay 1.1.2. This relay in operating .closes a circuit to battery for the operation ot relay 11 as tolloyvs: Battery, right-hand armature and front contact ot relay 147, inner ri eht-hand armature and front contact ot relay 112, lead 37, iniddle upper arn'iature and front, contact ot relay 1S, Winding;` ot relay 11, armature and back contact ot tripping relay 40 to ground at .lower outer arinature and baek contact et relay 4S. Relay 11- in operating' prepares a locking,r circuit 'tor itself 'from battery, through its upper armature and 'trout contact, to ground at the armature and back contact olf relay Lt8. Relay 11. in operating, by open in e' its inako-lietore-ln'eak contacts to battery opens the holding, circuit for relays 9 and 18 which vill new be released to disconnect leads 25, 2i', 28, 3G, 37 an d 3S troni the trunk ST to. disconnectI the conineon ringing` key equipment troni the trunk. It should be noted that a circuit tor the operation ot relay 11 also extends `through lower Winding` oit r-elay al1 te ground, thusI causing' this relay to operate and this relay in operating prepares the above mentioned locking circuits Ytor relays 43 and lelf.

YThus the operation o'f relay 1% prepares the rin gin g equipn'ient associated. with trunk ST for the transmission et signals 'tor callinf; party M on the desired line "-a'hen trunk ST is connected thereto and disconnects the rin ging key equipment an d the operatoi"s telephone set 'troni the trunk Relay 9 when released as liereinbetore described opens the circuit for the guard rlainp 12 to the equipment shown in Fie'. ,2 so this lainp Will nonv cease 'flashing and will be lighted steadily over a circuit as Vfollows: Battery, lamp 12, upper outer armature and back contact of relay 9, lower armature and back contact oit relay 48, upper outer armature and trent contact et relay 11, lou'eroutei.' armature and back contact of relay 1.0 to ground. The steady lighting` oit lainp l2 indicates to the B operator that the signaling equipment associated with trunk ST has been set in accordance with the operation of a ringing key.

It is evident troni the above description ot 'the Voperation of ringing equipment that the operation et any ot the rin ,ein e' keys 11i-1 to 1&3 or the trunk key. 144 will set up similar conditi ons in the ringing` equipment oit trunk ST by causing the operation ot' either or both ot the relays 13 and telin connection with the operation of relays 11 or no operation at all of any of these relays. For eXainple, the operation of key 144 will simply release the ringingl key equipment from the trunk.

As stated, lainp 12 is new lighted steadily to indicate that the trunk is ready for eXtension to the Wanted subscriber-s line. Hence, the B operator will now insert plug 4 into jack 5 of the desired line 3. This causes the operation ot relay 10 over the sleeve circuit. The operation ot this relay extends the tip conductor of the trunk ST through to the upper armature and back contact et relay 4:7 to `ground at the repeating coil 4S). The operation et this relay also extinguishes the guard lainp 12 by opening` the connection for this lanip through its outer armature and back cont-act. The operation ot relay 10 also causes the release ot relay 7. The release of relay 7 causes battery and ground to be conneeted at the repeating` coil .i9 for trunk ST to canse the lighting ot the usual supervisory signal in the cord circuit 1 at the toll operatoi"s position to in dieate to the toll operator that the ringing; equipment ot trunk ST .has been set tor the transmission et' a ringing sign al to the ufanted subseribeids line.

The tell. operator may now operate the usual ringing; key such as 55 to transmit an alternating eurren t signal to the trunk ST tor the operation ot its ringing equipment to transin't a ringing),l sig-nal to the Wanted subseribers line. This alternating current sig;- nal causes the operation ot relay 50 and this relay in operating closes circuits tor the op eration ot relay 7 and relay 51. Relay 7 in ieriperatingi prevents relay G and relay S 'troni releasing and displaying; the disconnect si gn al. The circuit tor relay 51 is as follows: Battery, Winding, and inalie-lietore-break contacts o't relay 51, ri glit-han d armature and back Contact ot relay 52, arnniture and trout contact oit relay 50 to ground. The operation of relay 10 and relay 51 also provides a locking circuit for relay l1 to prevent the release ot relays 43 and 11:4. Relay 51 provides a locking circuit for itself through its upper armature and 'trent contact to ground at the lower outer armature and back contact ot relay 1-S. The operationo't relay 51 closes a circuit tor the operation ot relay 4:7 as tollou's Frein battery at the upper inner arniature and front contact oit relay 10, lower inner armature and tronirontact et relay 51, upper Windingv of relay 47, lower inner arniature and itront contact ot relay 11, inner lower armature and 'trent contact ot relay 10, arma ture and front contact et relay 8 to 'ground Relay t7 in operating' applies the prepared ringing' signal to the tip and ring` conductors ot the trunk over plug' /1 and ack 5 to line 3. In this case ,if the party M is the party desired, rirgingjr current Ytron"A nource 4G is applied to the tip conductor and ground is connected to the ring` conductor as hereinbeliore described.

When the wanted subscriber answers this call by removing his receiver from the hook, ringing' trip relay 40 operates and this `relay in operating causes the release of relays 11 and 51. Relay 11 in releasing opens the circuit for the ringing relay 47, which now disconnects the ringing current from the line causing the releaseof the tripping relay 4() and closes a talking connection from the called subscriber to the repeating coil 49 and permits relay 53 to operate. The operation of relay closes a circuit through the middle winding of relay 7 which is now reoperated to extinguish the supervisory lainp in cord 1 to indicate to the toll operator that the wanted subscriber has answered the call. lt should be noted that the relay 7 will be released when the toll operator discontinues to send the alternating current signal causing the relighting of the supervisory signal at the toll cord at that time, but that relay 6 remains operated over the loop circuit in the toll operators cord 1. The operation of relay 53 also closes an obvious circuit for the operation of relay 52 which performs no useful function at this time but prepares the circuits for re'ringing the called subscriber as will hereinafter be described.

The toll operator will now complete the connection to the calling subscriber in the usual manner in toll practice and a conversa-y tion between the calling and called subscriber may then begin.

l/Vhen the conversation is ended and the called subscriber replaces his receiver on the hook, relay 53 releases causing in turn the release of relay 52 and relay 7. The release of relay 7 connects battery and ground to the tip and ring conductors of the trunk which causes the toll operators supervisory lamp to light as a disconnect signal. The toll operator will now remove the calling plug from jack 2 of trunk ST, thus causing the release of relays 6 and 8. Relay 8 in releasing permits relay 48 to operate over a circuit as follows Battery, inner upper armature and front contact of relay 10, winding of relay 48 to ground at the n'iake-beforebreak contacts of relay 8. Relay 48 in operat-ing closes a circuit for the lighting of lamp 12 as a disconnectV signal. The B operator will in answer to this signal remove plug 4 from jack 5, thus causing the release of relay 10 which in turn releases relay 48 to extinguish the disconnect lamp and restore the circuit to normal, that is, relay 41 is released and this relay in t-urn releases relays 48 and 44.

If it is desired to rering the called party after he has hung up his receiver the toll operator at A may do so by again operating relay 50. This relay in operating will reopeiate relays 7 and 51. The operation of relay 7 prevents relays 6 and 8 from releasing to display a disconnectsignal. Relay 51 in winding of relay 11, back operating causes the operation of relay 11 overa circuit as follows Battery, inner upper armature and front contact of relay 10, lower outer armature and front contact of relay 51, contact of relay 40, to ground at the lower armature and back contact of relay 48. Relay 11 in operating lprovides a locking circuit for itself through its limer upper armature and front contact to ground at the lower armature and back contact of relay 48. The operation of relay l1 causes relay 47 to operate and ringing currentis thus applied from source 46 to the tip conductor of the trunk and from ground to the ring conductor of the trunk since relays 43 and 44 remain operated due to the fact that relay 41 has been maintained operated under the control of relay 10.

If it is desired to rering the called party before he has restored the receiver on the hook, relay 50 is operated thus causing relay 47 to become operated due to the operation of relay 52 as hereinbefore described. Relay 52 is locked in operated position by the operation of relay 50, while relay 53 is released during the operation of relay 47.

It should be understood that the particular system shown merely illustrates one application of the invention and that this invention could be applied to other systems without departing from the spirit thereof.

Vha-t is claimed is:

1. In a telephone system, a plurality of trunks, lines for association with said trunks, a ringing key equipment and an operators telephone set common to said trunks, a key individual to each trunk, means responsive to the extension of a call to a trunk and to the actuation of the key individual to said trunk for associating' the ringing key equipment and the operators telephone set with said trunk, a ringing equipment individual to each trunk, the ringing equipment of a trunk being adapted to be set by the ringing key equipment for the transmission of a ringing signal when the ringing key equipment is associated with said trunk, means for disconnecting said operators telephone set and said ringing key equipment from said trunk effective after the ringing equipment has been set, means for sending a signal over said trunk, and means responsive to the reception of said signal over said trunk and to the connection of said trunk to a line for actuating the corresponding ringing equipment t0 transmit the ringing signal over said connected line.

2. In a telephone system, a trunk, a called line, a plurality of sources of ringing current, a ringing equipment individual to said trunk for selecting and poling said sources of ringing current, a ringing relay for applying said selected and poled ringing current to said trunk, a set of keys common to said trunk for setting said ringing equipment, a key individual to said trunk, and means jointly responsive to the seizure of said trunk and the `ectuation of said individual key for associatinsaid keys With said ringing equipment, means responsive to the setting or' said ringing equipment for disassociating said keys from said ringing equipment, means for sending a signal over said trunk, and means trunk to the said called line for actuating/said ringing relay.

In Witness whereof, I hereunto subscribe my name this 29th clay of November, A. D.

HAROLD D. CAHILL. 

